title: Enzymatic transamination of pyridoxamine in tobacco plants.
abstract: Vitamin B6 (VB6) comprises a group of pyridine compounds that are involved in a surprisingly high diversity of biochemical reactions. Humans and animals depend largely on plants for their VB6 nutrition. Many studies have focused on biosynthesis of VB6 and comparatively little is known about VB6 metabolic conversion in plants. Recently, we have found that an efficient conversion pathway between pyridoxal (PL) and pyridoxamine (PM) is present in tobacco, but the catalytic enzyme remains an unsolved mystery. In this study, enzymes catalyzing the transamination of PM were purified from tobacco leaves and characterized. Our results suggest that a specific PM-pyruvate aminotranferase dominates the reversible transamination of PM in tobacco, and also show that the apo form of glutamic-oxaloacetic aminotranferase from tobacco, but not the holoenzyme, is able to catalyze the analogous transamination reaction between PM and either oxaloacetate or α-ketoglutarate. PM-pyruvate aminotranferase is involved in a degradation pathway for VB6 compounds in bacteria. Therefore, our study raises questions about whether the degradation pathway of VB6 exists in plants.
authors.affiliation: Key Laboratory of Tea Biochemistry & Biotechnology of Ministry of Education and Ministry of Agriculture, Anhui Agricultural University, Hefei 230036, People's Republic of China; Center for Cell and Gene Therapy, Takara Bio Inc., Seta 3-4-1, Otsu, Shiga 520-2193, Japan.
authors.forename: ShuoHao
authors.initials: S
authors.lastname: Huang
authors.forename: JianYun
authors.initials: J
authors.lastname: Zhang
authors.forename: Mei
authors.initials: M
authors.lastname: Wu
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wu
authors.forename: LongQuan
authors.initials: L
authors.lastname: Huang
mesh_terms: D000586:Amination; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011733:Pyridoxamine / Q000378:metabolism*; D014026:Nicotiana / Q000201:enzymology / Q000378:metabolism*; D000637:Transaminases / Q000302:isolation & purification / Q000378:metabolism*; D025101:Vitamin B 6 / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D011733:Pyridoxamine; D025101:Vitamin B 6; D000637:Transaminases
keywords: Characterization; Glutamic-oxaloacetic aminotranferase; Nicotiana tabacum; Purification; Pyridoxamine-pyruvate aminotranferase